So i have a 1998 honda civic lx and i went to the shop to get my CEL checked out and they said it was my o2 sensor in bank 1 so i replaced it and went back to the shop to have my computer reset and after driving about 20 miles my light came back on and i went to the shop again and it says that my car still needs to o2 sensor in bank 1 and i dont know what to do anymore i replaced both sensors. my wires arent rusty or weathered. i forget twhat the code it but all it says is its a slow sensor but its new
CEL Still on after replacing o2 sensor
- Thread starter brendon17370
- Start date
what was the code? do you have an aftermarket header and/or test pipe?
the reading on the secondary sensor must be lower than the primary sensor. if you have a header and a test pipe/high flow cat, the airflow is much faster making the computer think that one of the sensors is slow because the reading on the sensors will be the same or close. you can trick the computer by putting a spacer on your secondary sensor so less air passes by the second one.
and you most likely didn't need a new sensor.
the reading on the secondary sensor must be lower than the primary sensor. if you have a header and a test pipe/high flow cat, the airflow is much faster making the computer think that one of the sensors is slow because the reading on the sensors will be the same or close. you can trick the computer by putting a spacer on your secondary sensor so less air passes by the second one.
and you most likely didn't need a new sensor.
everything is stock except my cold air intake.. i got a new catalyitic converter as well. how can i trick the computer? or how can i put a spacer.? please teach me ^_^ im a noob at this stuff..
theres two o2 sensors and one is on top of the manifold and theres another one on the catalytic converter which is under the manifold but even before i got a new converter it still said i needed a new o2 sensor
i dont remmeber the code ill try to get it again
does that affect the oil mixture or anything like that?
It's not too surprising you would have needed to replace the front HO2S and the catalytic converter together. A poorly running primary HO2S can throw the air:fuel mixture off, and this can damage or foul the catalytic converter. I just went through this with a 2000 EX, whose catalytic coverter was nearly completely clogged after a front HO2S failed (at least, I assume that's the order of events; I bought the vehicle post-failure as a fixer-upper)
On a 6th gen Civic ECU, I believe the secondary heater O2 sensor mostly just verifies the catalytic converter is working, e.g.: it doesn't influence the fuel trims, just helps verify emissions health. You shouldn't need a anti-fouler if you're on a completely stock setup, but maybe the replacement catalytic converter is higher flow or otherwise different from OE spec such that it could require such a setup.
You mentioned a slow response in sensor code, which would be P0133 for the primary (front) HO2S and P0139 for the secondary (rear) HO2S. Was this the code you started with, the code you were told after getting the new sensors, or did you actually see this result both times? Why did you replace both HO2S probes at once? What was the brand/model of the front and rear replacement sensors (they are each different part numbers)? If it wasn't Denso brand (for example, if it were a Bosch sensor), it may simply not be working to OE spec...
On a 6th gen Civic ECU, I believe the secondary heater O2 sensor mostly just verifies the catalytic converter is working, e.g.: it doesn't influence the fuel trims, just helps verify emissions health. You shouldn't need a anti-fouler if you're on a completely stock setup, but maybe the replacement catalytic converter is higher flow or otherwise different from OE spec such that it could require such a setup.
You mentioned a slow response in sensor code, which would be P0133 for the primary (front) HO2S and P0139 for the secondary (rear) HO2S. Was this the code you started with, the code you were told after getting the new sensors, or did you actually see this result both times? Why did you replace both HO2S probes at once? What was the brand/model of the front and rear replacement sensors (they are each different part numbers)? If it wasn't Denso brand (for example, if it were a Bosch sensor), it may simply not be working to OE spec...
Yeah i bought the car off of someone and he said the same thing to me but when i bought the car it had two codes so it said to change the cat conveter and o2 sensor so i did that and now my car just says it needs to o2 sensor bank 1 and yeah its the code P0133 that looks familiar. that was the code i started with.. i saw the result both times. the sensor in bank 1 was good still so i put it in bank 2. they are bosch.
i shouldnt need to do any modifications either since its stock. all i did was add a little washer to the o2 sensor this time to give it like a 2cm gap ill see if it does anything